Monitors Flashcards
How must we measure oxygenation (3)
- FiO2 analyzer
- Low [O2] alarm
- Pulse ox w/ variable pitch tone
How must we measure ventilation (2)
- Continuous capnography
- Disconnect alarm for vent
How must we measure circulation (3)
- EKG (3 or 5 leads)
- Blood pressure q5m
- ONE continuous measurement (pulse ox, a line, palpable pulse, auscultation, doppler)
When must we monitor temp
If significant changes are anticipated
How does pulse ox determine oxygenation?
- Light emitted at 660 (red, Hb) and 940 (infrared, HbO2) -> measures light absorbed
- Absorption during DC flow (non-pulsatile) is removed (aka venous, capillary, tissue flow)
How is SpO2 calculated?
S value = (AC/DC 660)/(AC/DC 940)
Why is a pulse ox not on a patient 85%?
1:1 ratio S value = 85%
Methemoglobin - how does SpO2 read?
- Approaches 85% (similar absorption at both wavelengths)
- Will appear falsely low if it’s actually > 85
- Will appear falsely high if it’s actually < 85
Carboxyhemoglobin - how does SpO2 read?
Falsely high (reads similar to HbO2)
What causes falsely low SpO2? (6)
- blue/green dyes
- blue nail polish
- shivering/motion
- ambient light
- low perfusion (low CO, anemia, hypothermia, etc)
- Mal-positioned sensor
SaO2 vs SpO2
SaO2 = HbO2 / ALL Hb
SpO2 = HbO2/(Hb + HbO2)
Things that DON’T affect SpO2
- Bilirubin
- HbF/HbS/SuHb
- acrylic nails
- flourescein dye (yellow-green)
When is cyanosis clinically seen?
With 5 g/dl desaturated Hb
- At Hb 15 -> 80% SpO2
- At Hb 9 -> 66% SpO2
Best lead for P waves and sinus rhythm
II
How to monitor for anterior ischemia w/ 3-lead EKG
Move L arm to V5 position, monitor lead I
Where does V5 lead go?
L anterior axillary line, 5th ICS
5-lead EKG - what can be monitored?
7 simultaneous leads
5-lead EKG - how to detect ischemia? (3) (least-most sensitive)
- V5 = 75%
- II + V5 = 80%
- II + V4 + V5 = 98%
How does NIBP work?
Measures oscillations in blood flow across different cuff pressures
– loudest oscillation pressure = MAP
Indications for invasive BP monitor (5)o a
- Moment-to-moment BP changes
- Planned pharm or mechanical manipulation
- Repeated blood sampling
- Failure of NIBP
- Measure volume status (via pulse pressure)
How does SBP and MAP change in aorta vs peripheral?
- SBP higher in periphery 2/2 reflected waves
- MAP is unchanged b/c higher SBP is offset by more time at diastolic pressure (“narrowing of systolic pressure wave”)
How does BP change based on vertical height?
pH = 7.410
Change in pressure (p) of 7.4 mmHg for every 10cm of height (H) difference
Up-sloping end tidal trace
Bronchospasm
Significant hypotension can lead to a ___ in EtCO2
Decrease
EtCO2 and PaCO2 in pulmonary embolism
Decreased EtCO2, but PaCO2 decreases more (hence, increased A-a gradient)
EtCO2 goal in CPR
> 10
Exhausted CO2 absorbant…EtCO2?
Does not return to 0-5
Apnea…EtCO2 trend?
Up 6 in first minute, then up 3 every minute after
Gold standard temperature location
Pulmonary artery
Tympanic membrane temp
Correlates w/ core well, approximates brain temp
Nasopharynx temp
Correlates well w/ core and brain
Oropharynx temp
Correlates well w/ core, tympanic, and esophagus
Esophagus temp
Correlates well w/ core
Bladder temp
Accurate when urine flow is high, but may be delay from core temp
Axillary temp
Inconsistent, varies by skin temp/perfusion
Rectal temp
Not accurate, affected by stool and venous blood and enteric organisms
Skin temp
Inaccurate, varies by site
Primary mode of heat loss
How do anesthetics cause heat loss?
Radiation (60%)
Vasodilation
